Identifying tile from network abstraction unit header

ABSTRACT

A method and apparatus for video decoding includes decoding a binary coded syntax element carrying an identification of a picture segment in a high level syntax structure comprising fixed length codewords and reconstructing the picture segment.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation of U.S. patent application Ser. No.16/403,799, filed May 6, 2019 in the United States Patent & TrademarkOffice, which claims priority under 35 U.S.C. § 119 to U.S. ProvisionalApplication No. 62/783,152, filed Dec. 20, 2018 in the United StatesPatent & Trademark Office, the disclosures of which are incorporatedherein by reference in their entireties.

FIELD

The disclosed subject matter relates to video coding and decoding, andmore specifically, to the inclusion of tile identifying information in afixed-length codepoint, high level syntax structure such as the NetworkAbstraction Layer unit header.

BACKGROUND

Video coding and decoding using inter-picture prediction with motioncompensation has been known for decades. Uncompressed digital video canconsist of a series of pictures, each picture having a spatial dimensionof, for example, 1920×1080 luminance samples and associated chrominancesamples. The series of pictures can have a fixed or variable picturerate (informally also known as frame rate), of, for example 60 picturesper second or 60 Hz. Uncompressed video has significant bitraterequirements. For example, 1080p60 4:2:0 video at 8 bit per sample(1920×1080 luminance sample resolution at 60 Hz frame rate) requiresclose to 1.5 Gbit/s bandwidth. An hour of such video requires more than600 GByte of storage space.

One purpose of video coding and decoding can be the reduction ofredundancy in the input video signal, through compression. Compressioncan help reducing aforementioned bandwidth or storage spacerequirements, in some cases by two orders of magnitude or more. Bothlossless and lossy compression, as well as a combination thereof can beemployed. Lossless compression refers to techniques where an exact copyof the original signal can be reconstructed from the compressed originalsignal. When using lossy compression, the reconstructed signal may notbe identical to the original signal, but the distortion between originaland reconstructed signal is small enough to make the reconstructedsignal useful for the intended application. In the case of video, lossycompression is widely employed. The amount of distortion tolerateddepends on the application; for example, users of certain consumerstreaming applications may tolerate higher distortion than users oftelevision contribution applications. The compression ratio achievablecan reflect that: higher allowable/tolerable distortion can yield highercompression ratios.

A video encoder and decoder can utilize techniques from several broadcategories, including, for example, motion compensation, transform,quantization, and entropy coding, some of which will be introducedbelow.

The concept of dividing a coded video bitstream into packets fortransportation over packet networks has been in use for decades. Earlyon, video coding standards and technologies were in their majorityoptimized for bit-oriented transport, and defined bitstreams.Packetization occurred in system layer interfaces specified, forexample, in Real-time Transport Protocol (RTP) payload formats. With theadvent of Internet connectivity suitable for mass-use of video over theInternet, the video coding standards reflected that prominent use casethrough the conceptual differentiation of a video coding layer (VCL) anda network abstraction layer (NAL). NAL units were introduced in H.264 in2003, and have been retained in certain video coding standards andtechnologies since then with only slight modifications.

A NAL unit can, in many cases, be seen as the smallest entity on which adecoder can act upon without necessarily having decoded all precedingNAL units of a coded video sequence. Insofar, NAL units enable certainerror resilience technologies as well as certain bitstream manipulationtechniques, to include bitstream pruning, by Media Aware NetworkElements (MANEs) such as Selective Forwarding Units (SFUs) or MultipointControl Units (MCUs).

FIG. 1 depicts relevant parts of the syntax diagram of NAL unit headersin accordance with H.264 (101) and H.265 (102), in both cases withoutany of their respective extensions. In both cases, the“forbidden_zero_bit” is a zero bit used for start code emulationprevention in certain system layer environments. The “nal_unit_typesyntax” element refers to the type of data a NAL unit carries, which canbe, for example, one of certain slice types, parameter set types,Supplementary Enhancement Information (SEI) message, and so on. TheH.265 NAL unit header further comprises “nuh_layer_id” and“nuh_temporal_id_plus1,” which indicate the spatial/SNR and temporallayer of a coded picture to which the NAL unit belongs.

It can be observed that the NAL unit header includes only easilyparseable fixed length codewords, that do not have any parsingdependency to other data in the bitstream such as, for example, otherNAL unit headers, parameter sets, and so on. As NAL unit headers are thefirst octets in a NAL unit, MANEs can easily extract them, parse them,and act on them. Other high level syntax elements, for example slice ortile headers, in contrast, are less easily accessible to MANEs as theymay require keeping parameter set context and/or the processing ofvariable length or arithmetically coded codepoints. However, evenstructures such as tile group headers could be designed to haveproperties that makes them easily accessible to MANEs, though existingvideo compression technologies and standards may not have done so.

It can further be observed that the NAL unit headers as shown in FIG. 1do not include information that can associate a NAL unit to a segment ofthe coded picture, such as a slice, tile, or similar part of thebitstream representing a spatial area of the coded picture. In therelated art, such information is present in the slice header, in certaincases in the form of a macroblock or CU address. That address, in somecases, is an integer number n indicating that a segment, slice, tile,starts at the n-th macroblock/CU in scan order when counting from thetop-left of the picture. Accordingly, n can be dependent on both pictureand macroblock/CU size, and can be small (e.g., fitting into 8 bits inbinary code) for small picture sizes or large (e.g., 32400, requiring 16bits in binary code); in both cases a macroblock/CU size of 16×16samples is assumed.

Historically, picture segments such as tiles or slices were used mostlyto facilitate bitstream partitioning to match Maximum Transfer Unit sizeconstraints, and parallelization. In both cases, an identification of atile or slice in a MANE, SFU, or similar device was normally notrequired. Decoders can obtain the relevant information from the,comparatively complex, slice header and/or similar information, inconjunction with state obtained from the decoding of parameter sets.

However, more recently, picture segments and especially tiles (and tilegroups, which are a collection of tiles in scan order, rectangularorder, or any other suitable order) have been used for purposes such asthe collecting of CUs representing certain views in composed 360projections, among other applications. In some of those applications,MANEs and SFUs can advantageously remove certain tiles or other segmentsfrom a coded picture when not required for an application. For example,when a cube projection is in use, rendering the scene from an outsideviewpoint requires at most three of the six cube surfaces. Transmitting,to an endpoint, the CUs and segments representing the remaining minimumthree surfaces can be a waste of resources. However, in scenarios wherea sender may send a full representation (including all six surfaces of acube projection) to a MANE, and the MANE forwards only the requiredsubset to potentially multiple receivers, and where that required subsetmay differ from receiver to receiver, the MANE would tailor potentiallydifferent bitstreams containing potentially different cube surfaces foreach receiver. Doing so, at present, requires the MANE to handle thecomplex variable length coded slice header as well as keeping state inthe form of parameter sets and the like, as required to decode the sliceheader.

SUMMARY

Disclosed are techniques for the inclusion of a tile identification in asyntax structure comprising fixed length codewords in a video codec, topermit improved identification of tiles based on the syntax structure.

A method for video decoding includes decoding a binary coded syntaxelement carrying an identification of a picture segment in a high levelsyntax structure comprising fixed length codewords; and reconstructingthe picture segment.

A device for decoding a video sequence, includes at least one memoryconfigured to store program code; at least one processor configured toread the program code and operate as instructed by the program code, theprogram code including: decoding code configure to cause the at leastone processor to decode a binary coded syntax element carrying anidentification of a picture segment in a high level syntax structurecomprising fixed length codewords; and reconstructing code configured tocause the at least one processor to reconstruct the picture segment.

A non-transitory computer-readable medium storing instructions, theinstructions comprising: one or more instructions that, when executed byone or more processors of a device, cause the one or more processors to:decode a binary coded syntax element carrying an identification of apicture segment in a high level syntax structure comprising fixed lengthcodewords; and reconstruct the picture segment.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, the nature, and various advantages of the disclosedsubject matter will be more apparent from the following detaileddescription and the accompanying drawings in which:

FIG. 1 is a schematic illustration of NAL Unit Headers in accordancewith H.264 and H.265.

FIG. 2 is a schematic illustration of a simplified block diagram of acommunication system in accordance with an embodiment.

FIG. 3 is a schematic illustration of a simplified block diagram of acommunication system in accordance with an embodiment.

FIG. 4 is a schematic illustration of a simplified block diagram of adecoder in accordance with an embodiment.

FIG. 5 is a schematic illustration of a simplified block diagram of anencoder in accordance with an embodiment.

FIG. 6 is a schematic illustration of a NAL unit header comprising a CUAddress or Tile ID syntax element in accordance with an embodiment.

FIG. 7 is a schematic illustration of a tile layout in accordance withan embodiment.

FIG. 8 is a schematic illustration of a NAL unit decoding/forwarding inaccordance with an embodiment.

FIG. 9 is a schematic illustration of a computer system in accordancewith an embodiment.

PROBLEM TO BE SOLVED

Video coding syntax lacks easily identifiable/parseable syntax elementsidentifying a tile or other picture segment in high level syntaxstructures such as NAL unit headers.

DETAILED DESCRIPTION

FIG. 2 illustrates a simplified block diagram of a communication system(200) according to an embodiment of the present disclosure. The system(200) may include at least two terminals (210-220) interconnected via anetwork (250). For unidirectional transmission of data, a first terminal(210) may code video data at a local location for transmission to theother terminal (220) via the network (250). The second terminal (220)may receive the coded video data of the other terminal from the network(250), decode the coded data and display the recovered video data.Unidirectional data transmission may be common in media servingapplications and the like.

FIG. 2 illustrates a second pair of terminals (230, 240) provided tosupport bidirectional transmission of coded video that may occur, forexample, during videoconferencing. For bidirectional transmission ofdata, each terminal (230, 240) may code video data captured at a locallocation for transmission to the other terminal via the network (250).Each terminal (230, 240) also may receive the coded video datatransmitted by the other terminal, may decode the coded data and maydisplay the recovered video data at a local display device.

In FIG. 2 , the terminals (210-240) may be illustrated as servers,personal computers and smart phones but the principles of the presentdisclosure may be not so limited. Embodiments of the present disclosurefind application with laptop computers, tablet computers, media playersand/or dedicated video conferencing equipment. The network (250)represents any number of networks that convey coded video data among theterminals (210-240), including for example wireline and/or wirelesscommunication networks. The communication network (250) may exchangedata in circuit-switched and/or packet-switched channels. Representativenetworks include telecommunications networks, local area networks, widearea networks and/or the Internet. For the purposes of the presentdiscussion, the architecture and topology of the network (250) may beimmaterial to the operation of the present disclosure unless explainedherein below.

FIG. 3 illustrates, as an example for an application for the disclosedsubject matter, the placement of a video encoder and decoder in astreaming environment. The disclosed subject matter can be equallyapplicable to other video enabled applications, including, for example,video conferencing, digital TV, storing of compressed video on digitalmedia including CD, DVD, memory stick and the like, and so on.

A streaming system may include a capture subsystem (313), that caninclude a video source (301), for example a digital camera, creating afor example uncompressed video sample stream (302). That sample stream(302), depicted as a bold line to emphasize a high data volume whencompared to encoded video bitstreams, can be processed by an encoder(303) coupled to the camera (301). The encoder (303) can includehardware, software, or a combination thereof to enable or implementaspects of the disclosed subject matter as described in more detailbelow. The encoded video bitstream (304), depicted as a thin line toemphasize the lower data volume when compared to the sample stream, canbe stored on a streaming server (305) for future use. One or morestreaming clients (306, 308) can access the streaming server (305) toretrieve copies (307, 309) of the encoded video bitstream (304). Aclient (306) can include a video decoder (310) which decodes theincoming copy of the encoded video bitstream (307) and creates anoutgoing video sample stream (311) that can be rendered on a display(312) or other rendering device (not depicted). In some streamingsystems, the video bitstreams (304, 307, 309) can be encoded accordingto certain video coding/compression standards. Examples of thosestandards include ITU-T Recommendation H.265. Under development is avideo coding standard informally known as Versatile Video Coding or VVC.The disclosed subject matter may be used in the context of VVC.

FIG. 4 may be a functional block diagram of a video decoder (310)according to an embodiment of the present invention.

A receiver (410) may receive one or more codec video sequences to bedecoded by the decoder (310); in the same or another embodiment, onecoded video sequence at a time, where the decoding of each coded videosequence is independent from other coded video sequences. The codedvideo sequence may be received from a channel (412), which may be ahardware/software link to a storage device which stores the encodedvideo data. The receiver (410) may receive the encoded video data withother data, for example, coded audio data and/or ancillary data streams,that may be forwarded to their respective using entities (not depicted).The receiver (410) may separate the coded video sequence from the otherdata. To combat network jitter, a buffer memory (415) may be coupled inbetween receiver (410) and entropy decoder/parser (420) (“parser”henceforth). When receiver (410) is receiving data from a store/forwarddevice of sufficient bandwidth and controllability, or from anisosychronous network, the buffer (415) may not be needed, or can besmall. For use on best effort packet networks such as the Internet, thebuffer (415) may be required, can be comparatively large and canadvantageously of adaptive size.

The video decoder (310) may include an parser (420) to reconstructsymbols (421) from the entropy coded video sequence. Categories of thosesymbols include information used to manage operation of the decoder(310), and potentially information to control a rendering device such asa display (312) that is not an integral part of the decoder but can becoupled to it, as was shown in FIG. 3 . The control information for therendering device(s) may be in the form of Supplementary EnhancementInformation (SEI messages) or Video Usability Information (VUI)parameter set fragments (not depicted). The parser (420) mayparse/entropy-decode the coded video sequence received. The coding ofthe coded video sequence can be in accordance with a video codingtechnology or standard, and can follow principles well known to a personskilled in the art, including variable length coding, Huffman coding,arithmetic coding with or without context sensitivity, and so forth. Theparser (420) may extract from the coded video sequence, a set ofsubgroup parameters for at least one of the subgroups of pixels in thevideo decoder, based upon at least one parameters corresponding to thegroup. Subgroups can include Groups of Pictures (GOPs), pictures, tiles,slices, macroblocks, Coding Units (CUs), blocks, Transform Units (TUs),Prediction Units (PUs) and so forth. The entropy decoder/parser may alsoextract from the coded video sequence information such as transformcoefficients, quantizer parameter values, motion vectors, and so forth.

The parser (420) may perform entropy decoding/parsing operation on thevideo sequence received from the buffer (415), so to create symbols(421).

Reconstruction of the symbols (421) can involve multiple different unitsdepending on the type of the coded video picture or parts thereof (suchas: inter and intra picture, inter and intra block), and other factors.Which units are involved, and how, can be controlled by the subgroupcontrol information that was parsed from the coded video sequence by theparser (420). The flow of such subgroup control information between theparser (420) and the multiple units below is not depicted for clarity.

Beyond the functional blocks already mentioned, decoder 310 can beconceptually subdivided into a number of functional units as describedbelow. In a practical implementation operating under commercialconstraints, many of these units interact closely with each other andcan, at least partly, be integrated into each other. However, for thepurpose of describing the disclosed subject matter, the conceptualsubdivision into the functional units below is appropriate.

A first unit is the scaler/inverse transform unit (451). Thescaler/inverse transform unit (451) receives quantized transformcoefficient as well as control information, including which transform touse, block size, quantization factor, quantization scaling matrices,etc. as symbol(s) (421) from the parser (420). It can output blockscomprising sample values, that can be input into aggregator (455).

In some cases, the output samples of the scaler/inverse transform (451)can pertain to an intra coded block; that is: a block that is not usingpredictive information from previously reconstructed pictures, but canuse predictive information from previously reconstructed parts of thecurrent picture. Such predictive information can be provided by an intrapicture prediction unit (452). In some cases, the intra pictureprediction unit (452) generates a block of the same size and shape ofthe block under reconstruction, using surrounding already reconstructedinformation fetched from the current (partly reconstructed) picture(456). The aggregator (455), in some cases, adds, on a per sample basis,the prediction information the intra prediction unit (452) has generatedto the output sample information as provided by the scaler/inversetransform unit (451).

In other cases, the output samples of the scaler/inverse transform unit(451) can pertain to an inter coded, and potentially motion compensatedblock. In such a case, a Motion Compensation Prediction unit (453) canaccess reference picture memory (457) to fetch samples used forprediction. After motion compensating the fetched samples in accordancewith the symbols (421) pertaining to the block, these samples can beadded by the aggregator (455) to the output of the scaler/inversetransform unit (in this case called the residual samples or residualsignal) so to generate output sample information. The addresses withinthe reference picture memory form where the motion compensation unitfetches prediction samples can be controlled by motion vectors,available to the motion compensation unit in the form of symbols (421)that can have, for example X, Y, and reference picture components.Motion compensation also can include interpolation of sample values asfetched from the reference picture memory when sub-sample exact motionvectors are in use, motion vector prediction mechanisms, and so forth.

The output samples of the aggregator (455) can be subject to variousloop filtering techniques in the loop filter unit (456). Videocompression technologies can include in-loop filter technologies thatare controlled by parameters included in the coded video bitstream andmade available to the loop filter unit (456) as symbols (421) from theparser (420), but can also be responsive to meta-information obtainedduring the decoding of previous (in decoding order) parts of the codedpicture or coded video sequence, as well as responsive to previouslyreconstructed and loop-filtered sample values.

The output of the loop filter unit (456) can be a sample stream that canbe output to the render device (312) as well as stored in the referencepicture memory (456) for use in future inter-picture prediction.

Certain coded pictures, once fully reconstructed, can be used asreference pictures for future prediction. Once a coded picture is fullyreconstructed and the coded picture has been identified as a referencepicture (by, for example, parser (420)), the current reference picture(456) can become part of the reference picture buffer (457), and a freshcurrent picture memory can be reallocated before commencing thereconstruction of the following coded picture.

The video decoder 420 may perform decoding operations according to apredetermined video compression technology that may be documented in astandard, such as ITU-T Rec. H.265. The coded video sequence may conformto a syntax specified by the video compression technology or standardbeing used, in the sense that it adheres to the syntax of the videocompression technology or standard, as specified in the videocompression technology document or standard and specifically in theprofiles document therein. Also necessary for compliance can be that thecomplexity of the coded video sequence is within bounds as defined bythe level of the video compression technology or standard. In somecases, levels restrict the maximum picture size, maximum frame rate,maximum reconstruction sample rate (measured in, for example megasamplesper second), maximum reference picture size, and so on. Limits set bylevels can, in some cases, be further restricted through HypotheticalReference Decoder (HRD) specifications and metadata for HRD buffermanagement signaled in the coded video sequence.

In an embodiment, the receiver (410) may receive additional (redundant)data with the encoded video. The additional data may be included as partof the coded video sequence(s). The additional data may be used by thevideo decoder (420) to properly decode the data and/or to moreaccurately reconstruct the original video data. Additional data can bein the form of, for example, temporal, spatial, or SNR enhancementlayers, redundant slices, redundant pictures, forward error correctioncodes, and so on.

FIG. 5 may be a functional block diagram of a video encoder (303)according to an embodiment of the present disclosure.

The encoder (303) may receive video samples from a video source (301)(that is not part of the encoder) that may capture video image(s) to becoded by the encoder (303).

The video source (301) may provide the source video sequence to be codedby the encoder (303) in the form of a digital video sample stream thatcan be of any suitable bit depth (for example: 8 bit, 10 bit, 12 bit, .. . ), any colorspace (e.g., BT.601 Y CrCB, RGB, and/or the like) andany suitable sampling structure (e.g., Y CrCb 4:2:0, Y CrCb 4:4:4). In amedia serving system, the video source (301) may be a storage devicestoring previously prepared video. In a videoconferencing system, thevideo source (303) may be a camera that captures local image informationas a video sequence. Video data may be provided as a plurality ofindividual pictures that impart motion when viewed in sequence. Thepictures themselves may be organized as a spatial array of pixels,wherein each pixel can comprise one or more sample depending on thesampling structure, color space, etc. in use. A person skilled in theart can readily understand the relationship between pixels and samples.The description below focusses on samples.

According to an embodiment, the encoder (303) may code and compress thepictures of the source video sequence into a coded video sequence (543)in real time or under any other time constraints as required by theapplication. Enforcing appropriate coding speed is one function ofController (550). Controller controls other functional units asdescribed below and is functionally coupled to these units. The couplingis not depicted for clarity. Parameters set by controller can includerate control related parameters (picture skip, quantizer, lambda valueof rate-distortion optimization techniques, and/or the like), picturesize, group of pictures (GOP) layout, maximum motion vector searchrange, and so forth. A person skilled in the art can readily identifyother functions of controller (550) as they may pertain to video encoder(303) optimized for a certain system design.

Some video encoders operate in what a person skilled in the are readilyrecognizes as a “coding loop.” As an oversimplified description, acoding loop can consist of the encoding part of an encoder (530)(“source coder” henceforth) (responsible for creating symbols based onan input picture to be coded, and a reference picture(s)), and a (local)decoder (533) embedded in the encoder (303) that reconstructs thesymbols to create the sample data a (remote) decoder also would create(as any compression between symbols and coded video bitstream islossless in the video compression technologies considered in thedisclosed subject matter). That reconstructed sample stream is input tothe reference picture memory (534). As the decoding of a symbol streamleads to bit-exact results independent of decoder location (local orremote), the reference picture buffer content is also bit exact betweenlocal encoder and remote encoder. In other words, the prediction part ofan encoder “sees” as reference picture samples exactly the same samplevalues as a decoder would “see” when using prediction during decoding.This fundamental principle of reference picture synchronicity (andresulting drift, if synchronicity cannot be maintained, for examplebecause of channel errors) is well known to a person skilled in the art.

The operation of the “local” decoder (533) can be the same as of a“remote” decoder (310), which has already been described in detail abovein conjunction with FIG. 4 . Briefly referring also to FIG. 4 , however,as symbols are available and en/decoding of symbols to a coded videosequence by entropy coder (545) and parser (420) can be lossless, theentropy decoding parts of decoder (310), including channel (412),receiver (410), buffer (415), and parser (420) may not be fullyimplemented in local decoder (533).

An observation that can be made at this point is that any decodertechnology except the parsing/entropy decoding that is present in adecoder also necessarily needs to be present, in substantially identicalfunctional form, in a corresponding encoder. For this reason, thedisclosed subject matter focusses on decoder operation. The descriptionof encoder technologies can be abbreviated as they are the inverse ofthe comprehensively described decoder technologies. Only in certainareas a more detail description is required and provided below.

As part of its operation, the source coder (530) may perform motioncompensated predictive coding, which codes an input frame predictivelywith reference to one or more previously-coded frames from the videosequence that were designated as “reference frames.” In this manner, thecoding engine (532) codes differences between pixel blocks of an inputframe and pixel blocks of reference frame(s) that may be selected asprediction reference(s) to the input frame.

The local video decoder (533) may decode coded video data of frames thatmay be designated as reference frames, based on symbols created by thesource coder (530). Operations of the coding engine (532) mayadvantageously be lossy processes. When the coded video data may bedecoded at a video decoder (not shown in FIG. 5 ), the reconstructedvideo sequence typically may be a replica of the source video sequencewith some errors. The local video decoder (533) replicates decodingprocesses that may be performed by the video decoder on reference framesand may cause reconstructed reference frames to be stored in thereference picture cache (534). In this manner, the encoder (303) maystore copies of reconstructed reference frames locally that have commoncontent as the reconstructed reference frames that will be obtained by afar-end video decoder (absent transmission errors).

The predictor (535) may perform prediction searches for the codingengine (532). That is, for a new frame to be coded, the predictor (535)may search the reference picture memory (534) for sample data (ascandidate reference pixel blocks) or certain metadata such as referencepicture motion vectors, block shapes, and so on, that may serve as anappropriate prediction reference for the new pictures. The predictor(535) may operate on a sample block-by-pixel block basis to findappropriate prediction references. In some cases, as determined bysearch results obtained by the predictor (535), an input picture mayhave prediction references drawn from multiple reference pictures storedin the reference picture memory (534).

The controller (550) may manage coding operations of the video coder(530), including, for example, setting of parameters and subgroupparameters used for encoding the video data.

Output of all aforementioned functional units may be subjected toentropy coding in the entropy coder (545). The entropy coder translatesthe symbols as generated by the various functional units into a codedvideo sequence, by loss-less compressing the symbols according totechnologies known to a person skilled in the art as, for exampleHuffman coding, variable length coding, arithmetic coding, and so forth.

The transmitter (540) may buffer the coded video sequence(s) as createdby the entropy coder (545) to prepare it for transmission via acommunication channel (560), which may be a hardware/software link to astorage device which would store the encoded video data. The transmitter(540) may merge coded video data from the video coder (530) with otherdata to be transmitted, for example, coded audio data and/or ancillarydata streams (sources not shown).

The controller (550) may manage operation of the encoder (303). Duringcoding, the controller (550) may assign to each coded picture a certaincoded picture type, which may affect the coding techniques that may beapplied to the respective picture. For example, pictures often may beassigned as one of the following frame types:

An Intra Picture (I picture) may be one that may be coded and decodedwithout using any other frame in the sequence as a source of prediction.Some video codecs allow for different types of Intra pictures,including, for example Independent Decoder Refresh Pictures. A personskilled in the art is aware of those variants of I pictures and theirrespective applications and features.

A Predictive picture (P picture) may be one that may be coded anddecoded using intra prediction or inter prediction using at most onemotion vector and reference index to predict the sample values of eachblock.

A Bi-directionally Predictive Picture (B Picture) may be one that may becoded and decoded using intra prediction or inter prediction using atmost two motion vectors and reference indices to predict the samplevalues of each block. Similarly, multiple-predictive pictures can usemore than two reference pictures and associated metadata for thereconstruction of a single block.

Source pictures commonly may be subdivided spatially into a plurality ofsample blocks (for example, blocks of 4×4, 8×8, 4×8, or 16×16 sampleseach) and coded on a block-by-block basis. Blocks may be codedpredictively with reference to other (already coded) blocks asdetermined by the coding assignment applied to the blocks' respectivepictures. For example, blocks of I pictures may be codednon-predictively or they may be coded predictively with reference toalready coded blocks of the same picture (spatial prediction or intraprediction). Pixel blocks of P pictures may be coded non-predictively,via spatial prediction or via temporal prediction with reference to onepreviously coded reference pictures. Blocks of B pictures may be codednon-predictively, via spatial prediction or via temporal prediction withreference to one or two previously coded reference pictures.

The video coder (303) may perform coding operations according to apredetermined video coding technology or standard, such as ITU-T Rec.H.265. In its operation, the video coder (303) may perform variouscompression operations, including predictive coding operations thatexploit temporal and spatial redundancies in the input video sequence.The coded video data, therefore, may conform to a syntax specified bythe video coding technology or standard being used.

In an embodiment, the transmitter (540) may transmit additional datawith the encoded video. The video coder (530) may include such data aspart of the coded video sequence. Additional data may comprisetemporal/spatial/SNR enhancement layers, other forms of redundant datasuch as redundant pictures and slices, Supplementary EnhancementInformation (SEI) messages, Visual Usability Information (VUI) parameterset fragments, and so on.

According to an embodiment, information identifying a picture segmentsuch as a tile, tile group, slice, Group Of Blocks (GOB), and so forth(tile henceforth) is placed in an easily accessible high level syntaxstructure such as the NAL Unit Header (NUH) or similar structurecomprising fixed length codewords and designed for easy processing byMANEs (NUH henceforth).

The information identifying a tile can take different forms. Indesigning this information, a few design considerations should be keptin mind. Some of these design considerations are listed below.

The possible number of tiles in a given picture can be small whencompared to, for example the possible number of slices in legacy videocoding technologies or standards. For example, in H.264, it is possible(for certain picture sizes) to have slices covering a single macroblock,allowing for as many slices as there are macroblocks. In contrast, whenrepresenting a tiled cube map, six tiles may suffice, independent of theresolution of the picture. In many practical cases, a maximum number oftiles of 64, 128, or 256 can safely be assumed.

The tile layout can be fixed and, while the video coding technologyitself may allow flexibility of the tile layout from picture to picture,system standards or technologies can restrict that flexibility to thepoint where a tile layout remains the same throughout a session. Thatcan allow the tile layout to be made available to a MANE throughnon-video bitstream specific means, such as during the session setup. Anundesirable context dependency between parameter sets in the videocoding and MANE operation can thereby be prohibited.

At least under the above assumptions, the mechanism to identify a tilecarried by NAL unit, so as to allow the NAL unit to be removed by aMANE, can be significantly simplified when compared to related art, suchas H.264 and H.265. For example, in H.264 and H.265, a MANE would haveto identify the correct sequence parameter set to learn about the lengthof the slice/tile address codeword in the slice header. Such lengthinformation is coded as a variable length codeword in the sequenceparameter set; therefore, at a minimum, a MANE would need to follow theactivation sequence of parameter sets to identify the currently activesequence parameter set, and (possibly not in this order, as parametersets are parsing-independent) decode variable length codewords toidentify the length of the binary coded slice/tile address in thecarried in the slice header. Then, the MANE would need to decodevariable length codeword(s) in the slice header in order to obtain thestarting macroblock/CU address. That information can be matched againstthe tile layout as decoded from the parameter sets to identify the tile.

In the same or another embodiment, the identification information forthe tile can be the address of the first macroblock/CU of the tile. Ineffect, such a mechanism would move the starting address from the sliceheader to the NUH. While doing so can be a minimum change approach tothe codec design, it has the disadvantage of growing the NUHsignificantly. However, that increase of the size of the NUH may betolerable even from a coding efficiency viewpoint, because the sameamount of bits would have been removed from the slice/tile headers.

As pointed out above, a macroblock/CU address can be reasonably smallfor small picture sizes and large macroblock/CU sizes, or quite largefor small CU sizes and large picture sizes. For this reason, H.265's SPScontains an indication of the length of the macroblock/CU address ascarried in the slice header. In the same or another embodiment, thatmechanism can be retained for the NAL unit header. However, doing so canhave two disadvantages. First, the context dependency established bydetermining the size of a syntax element in the NAL unit header througha parameter set value may require a MANE to keep track of parameter setactivation, which can be tedious. Second, NAL unit headers are, at leastuntil now, octet aligned to simplify processing in MANEs. Maintainingthat octet alignment may require padding—wasting bits—in such caseswhere the size of the macroblock/CU address as signaled by the parameterset, in conjunction with the remaining NAL unit header syntax elements,do not add up to a number in bits divisible by 8.

In the same or another embodiment, the size of the macroblock/CUaddress—or any other syntax element in the NAL unit header—can bedetermined by other fields in the NAL unit header. This mechanism avoidsthe context dependency between parameter sets and NAL unit headers andmay, in many cases, be preferable. The disadvantage can be the use ofbits, or codepoints, in other fields of the NAL unit header. Moredetails are provided below.

However, when not considering slices in the traditional sense, but onlytiles or tile groups or similar allocation mechanisms of CUs tobitstream entities, more advanced options can be available. In order todescribe those options, the term slice and tile shall briefly bereviewed. A slice can be a collection of CUs or macroblocks, normally inscan order, and identified by two factors: the starting macroblock/CUaddress, normally coded in the slice header, and the end of the slice,often identified by the start of a new slice (which, in turn isindicated through the presence of the next slice header). While certainvideo compression technologies and standards impose certain relativelyminor restrictions on the number and layout of slices, in most cases,the slice layout can change from coded picture to coded picture and isoften determined by mechanisms such as rate control and MTU sizematching.

Tiles, on the other hand, may refer to a typically rectangulararrangement of CUs, and the size and shape of the rectangle (where thatrectangular tile and other rectangular tiles, in combination make up thepicture) is coded in a parameter set. In other words, a tile layout issomewhat static in that a change from one tile layout to anotherrequires the activation of a different parameter set. Further, thenumber of tiles can advantageously be restricted so to enable efficienthardware implementations. The result can be that, in many videocompression technologies and standards, a relatively short fixed lengthbinary codeword of, for example, 8 bits, allows for addressing themaximum number of tiles for all picture sizes in practical use.Accordingly, a fixed length codeword for a tile ID can be used toidentify a tile in a NAL unit header, thereby avoiding a parsing andcontext dependency between the tile-identifying NAL unit header codewordand parameter sets. Similarly, a fixed length codeword for a tile groupID can be used to identify a tile group. Of course, the mechanismssupporting a variable length codeword for macroblock/CU addresses in theNAL unit header can, if so desired, equally applied to a tile IDcodeword, at the expense of similar architectural shortcomings.

Referring to FIG. 6 , a few implementation options for a NAL unit headerdesign are introduced.

A NAL unit (601) can be a part of a coded video bitstream. In somecases, a NAL unit is octet aligned and smaller or equal to a commonMaximum Transfer Unit (MTU) size of a data network. One such common MTUsize is approximately 1500 octets, which stems from certain limitationsof early Ethernet technologies. A NAL unit can include a NAL unit header(602), at its beginning. The framing of NAL units inside a coded videobitstream can be through start codes, through alignment with packetstructures of underlying packet oriented transport networks, and soforth.

Again referring to FIG. 6 , shown is also a syntax diagram (603) of anexemplary NAL unit header, similar to the one used in H.265. Thedisclosed subject matter can equally be employed with NAL unit headersof similar structure, for example the NAL unit header of H.264, or VVCor any other high level syntax structure comprising fixed lengthcodewords. In the NAL unit header (603), a syntax element CU Address orTile ID (604) can be included. The length of that syntax element can befixed, and can be chosen such that the NAL unit header continues to beoctet aligned. The syntax element (604) can be in a format easilyprocessable not only by video encoder and decoders, but also by MANEs.By way of example and not as a limitation, a CU address or a Tile ID(604) can be represented by an 6 bit unsigned integer, as expressed bythe Descriptor u(6). In the example presented, the CU Address or Tile IDoccupies the same bits that are used, in H.265, for the layer_id. Adifferent presentation of a similar subject matter is shown with NALunit header (605), and CU address or Tile ID (606).

Also shown is a NAL unit (607) which preserves the fields of the H.265NAL unit header. A syntax element (608) is added at, for example, theend of the NAL unit header. The position of that syntax element isexemplary only; it may also be inserted somewhere in the middle of theother syntax elements of the NAL unit header. That syntax element can beof fixed or variable size and, when of variable size, its size can bedetermined by any of the mechanisms mentioned above (e.g., through aparameter set syntax element, through the NAL unit type, and/or thelike), or any other appropriate mechanism.

The syntax element (608) can carry any form of picture segmentidentifying information; for example, a macroblock/CU address or tileidentification such as a tile number, or a number denoting a tile group.The numbering range for the syntax element can be pre-determined. Incase of a macroblock/CU address, the numbering range can be from 0 tothe maximum number of macroblocks/CUs in the picture. For tile IDs, thenumbering range can be dependent on the maximum number of tiles, whichcan be defined by mechanisms known to a person skilled in the art, suchas, for example, profiles, levels, tiers, maximum or actual picturesizes as coded in parameter sets, and so forth. If the syntax element ispresent for non-tile/slice NAL units (such as parameter set NAL units,SEI NAL units, or similar, then the value of the syntax element can berestricted to a certain number, for example 0. Alternatively, thepresence of the syntax element can be gated on the NAL unit type, and,thereby, the syntax element may not be present in certain NAL unittypes. Alternatively, an overriding semantic other than the onedescribed above can be assigned to the syntax element in case of certainnon-tile/slice NAL unit types.

In the same or another embodiment, a tile ID can be identified, forexample, as follows. FIG. 7 shows a picture (701) in the spatial domainthat is subdivided by exemplary tile layout (702) indicated throughboldface lines. The tile layout presented may be representable by syntaxas available in, for example H.265, or by more advanced syntax as itwould be needed to represent the tile layout (702). Each tile in thetile layout can have a tile ID assigned, through any appropriatenumbering mechanism but preferably through a scan order numbering oftiles. In FIG. 7 , scan order tile numbering is shown through tile IDs 1through 8; for example, the second tile in scan order has tile ID 2(703) assigned.

An encoder can write NAL unit headers including a syntax elementcovering a tile ID or a macroblock/CU address populated as describedabove in a manner similar to writing existing NAL unit header syntax,which is known to a person skilled in the art.

A decoder or MANE can parse, from a coded video bitstream, a NAL unitheader—more precisely—the syntax elements that make up the NAL unitheader—in a manner known to a person skilled in the art, irrespective ofthe presence or absence of a syntax element carrying macroblock/CUaddress or tile ID or other forms of tile-identifying information. Itshould be noted, however, that the syntax element, in some cases asdescribed above, may be coded without requiring state information andmay be in an accessible entropy coded format, for example a fixedlength, binary code. Insofar, parsing a NAL unit header according to thedisclosed subject matter may not include additional burdensome operationto decoder or MANE beyond the actual presence of the syntax elementtile_id itself.

In accordance with the disclosed subject matter, decoder or MANE can,however, identify a tile in a coded picture with little effort whencompared to the operations required absent the disclosed subject matter.As an example, assume a decoder or MANE has been informed by external,non-video coding means, that a certain tile is not required to bereconstructed for a certain application. For example, consider the sceneas shown in FIG. 7 , namely a street in a village. Assume that streethas been captured by a surveillance camera. Consider tile with tile ID 2(703). That tile covers mostly walls; assume that the configurator ofthe surveillance system considers that area not relevant forsurveillance. Accordingly, while the camera may be encoding all tiles,the tile with the ID 2 may not be required for the application.Accordingly, if the bitstream created by the camera were routed throughone or more MANEs to its final destination, and one MANE observesbandwidth shortages and has to remove something from the bitstream, itcould advantageously remove that tile as it may not be required for theapplication. Absent the disclosed subject matter, that would require, asa minimum, that payload of the NAL unit (slice or tile) be parsed, tothe extent required, to extract the macroblock/CU address of the firstmacroblock in the tile, then mapping that macroblock/CU address againsta tile layout (if tiles are in use). Depending on the video codingtechnology or standard in use, and as described above, that may requireboth the processing of variable length codewords and the keeping ofparameter set context in the MANE; both undesirable from animplementation and computational complexity viewpoint. Instead, in thesame or another embodiment, the MANE may obtain all informationnecessary to identify which tile is carried by the NAL unit through NALunit header processing of binary coded codewords.

Referring to FIG. 8 , a decoder or MANE can use the disclosed subjectmatter for example as follows.

The decoder may parse, from a video bitstream, a NAL unit headercomprising a syntax element covering a macroblock/CU address or tile ID(801). Using that information, the decoder or MANE can identify a tileID (802). The tile ID may be coded directly, or the decoder/MANE canmatch a priori information about the tile layout, as established forexample by decoding parameter sets and following activation sequences,with the macroblock/CU address coded in the NAL unit header. The decodercan match (803) the tile ID against a list of tiles that requirereconstruction or forwarding, by the decoder or MANE, respectively. Ifthere is a match (803), the decoder can reconstruct, or the MANE canforward, the NAL unit carrying the tile. If, however, there is no match(804), the decoder or MANE can, possibly silently, discard the NAL unit.

The techniques for Picture Reference in Network Abstraction Unit Headerdescribed above, can be implemented as computer software usingcomputer-readable instructions and physically stored in one or morecomputer-readable media. For example, FIG. 9 shows a computer system 900suitable for implementing certain embodiments of the disclosed subjectmatter.

The computer software can be coded using any suitable machine code orcomputer language, that may be subject to assembly, compilation,linking, or like mechanisms to create code comprising instructions thatcan be executed directly, or through interpretation, micro-codeexecution, and the like, by computer central processing units (CPUs),Graphics Processing Units (GPUs), and the like.

The instructions can be executed on various types of computers orcomponents thereof, including, for example, personal computers, tabletcomputers, servers, smartphones, gaming devices, internet of thingsdevices, and the like.

The components shown in FIG. 9 for computer system 900 are exemplary innature and are not intended to suggest any limitation as to the scope ofuse or functionality of the computer software implementing embodimentsof the present disclosure. Neither should the configuration ofcomponents be interpreted as having any dependency or requirementrelating to any one or combination of components illustrated in theexemplary embodiment of a computer system 900.

Computer system 900 may include certain human interface input devices.Such a human interface input device may be responsive to input by one ormore human users through, for example, tactile input (such as:keystrokes, swipes, data glove movements), audio input (such as: voice,clapping), visual input (such as: gestures), olfactory input (notdepicted). The human interface devices can also be used to capturecertain media not necessarily directly related to conscious input by ahuman, such as audio (such as: speech, music, ambient sound), images(such as: scanned images, photographic images obtain from a still imagecamera), video (such as two-dimensional video, three-dimensional videoincluding stereoscopic video).

Input human interface devices may include one or more of (only one ofeach depicted): keyboard 901, mouse 902, trackpad 903, touch screen 910,data-glove 904, joystick 905, microphone 906, scanner 907, camera 908.

Computer system 900 may also include certain human interface outputdevices. Such human interface output devices may be stimulating thesenses of one or more human users through, for example, tactile output,sound, light, and smell/taste. Such human interface output devices mayinclude tactile output devices (for example tactile feedback by thetouch-screen 910, data-glove 904, or joystick 905, but there can also betactile feedback devices that do not serve as input devices), audiooutput devices (such as: speakers 909, headphones (not depicted)),visual output devices (such as screens 910 to include CRT screens, LCDscreens, plasma screens, OLED screens, each with or without touch-screeninput capability, each with or without tactile feedback capability—someof which may be capable to output two dimensional visual output or morethan three dimensional output through means such as stereographicoutput; virtual-reality glasses (not depicted), holographic displays andsmoke tanks (not depicted)), and printers (not depicted).

Computer system 900 can also include human accessible storage devicesand their associated media such as optical media including CD/DVD ROM/RW920 with CD/DVD or the like media 921, thumb-drive 922, removable harddrive or solid state drive 923, legacy magnetic media such as tape andfloppy disc (not depicted), specialized ROM/ASIC/PLD based devices suchas security dongles (not depicted), and the like.

Those skilled in the art should also understand that term “computerreadable media” as used in connection with the presently disclosedsubject matter does not encompass transmission media, carrier waves, orother transitory signals.

Computer system 900 can also include interface to one or morecommunication networks. Networks can for example be wireless, wireline,optical. Networks can further be local, wide-area, metropolitan,vehicular and industrial, real-time, delay-tolerant, and so on. Examplesof networks include local area networks such as Ethernet, wireless LANs,cellular networks to include GSM, 3G, 4G, 5G, LTE and the like, TVwireline or wireless wide area digital networks to include cable TV,satellite TV, and terrestrial broadcast TV, vehicular and industrial toinclude CANBus, and so forth. Certain networks commonly require externalnetwork interface adapters that attached to certain general purpose dataports or peripheral buses (949) (such as, for example USB ports of thecomputer system 900; others are commonly integrated into the core of thecomputer system 900 by attachment to a system bus as described below(for example Ethernet interface into a PC computer system or cellularnetwork interface into a smartphone computer system). Using any of thesenetworks, computer system 900 can communicate with other entities. Suchcommunication can be uni-directional, receive only (for example,broadcast TV), uni-directional send-only (for example CANbus to certainCANbus devices), or bi-directional, for example to other computersystems using local or wide area digital networks. Certain protocols andprotocol stacks can be used on each of those networks and networkinterfaces as described above.

Aforementioned human interface devices, human-accessible storagedevices, and network interfaces can be attached to a core 940 of thecomputer system 900.

The core 940 can include one or more Central Processing Units (CPU) 941,Graphics Processing Units (GPU) 942, specialized programmable processingunits in the form of Field Programmable Gate Areas (FPGA) 943, hardwareaccelerators for certain tasks 944, and so forth. These devices, alongwith Read-only memory (ROM) 945, Random-access memory 946, internal massstorage such as internal non-user accessible hard drives, SSDs, and thelike 947, may be connected through a system bus 948. In some computersystems, the system bus 948 can be accessible in the form of one or morephysical plugs to enable extensions by additional CPUs, GPU, and thelike. The peripheral devices can be attached either directly to thecore's system bus 948, or through a peripheral bus 949. Architecturesfor a peripheral bus include PCI, USB, and the like.

CPUs 941, GPUs 942, FPGAs 943, and accelerators 944 can execute certaininstructions that, in combination, can make up the aforementionedcomputer code. That computer code can be stored in ROM 945 or RAM 946.Transitional data can be also be stored in RAM 946, whereas permanentdata can be stored for example, in the internal mass storage 947. Faststorage and retrieve to any of the memory devices can be enabled throughthe use of cache memory, that can be closely associated with one or moreCPU 941, GPU 942, mass storage 947, ROM 945, RAM 946, and the like.

The computer readable media can have computer code thereon forperforming various computer-implemented operations. The media andcomputer code can be those specially designed and constructed for thepurposes of the present disclosure, or they can be of the kind wellknown and available to those having skill in the computer software arts.

As an example and not by way of limitation, the computer system havingarchitecture 900, and specifically the core 940 can providefunctionality as a result of processor(s) (including CPUs, GPUs, FPGA,accelerators, and the like) executing software embodied in one or moretangible, computer-readable media. Such computer-readable media can bemedia associated with user-accessible mass storage as introduced above,as well as certain storage of the core 940 that are of non-transitorynature, such as core-internal mass storage 947 or ROM 945. The softwareimplementing various embodiments of the present disclosure can be storedin such devices and executed by core 940. A computer-readable medium caninclude one or more memory devices or chips, according to particularneeds. The software can cause the core 940 and specifically theprocessors therein (including CPU, GPU, FPGA, and the like) to executeparticular processes or particular parts of particular processesdescribed herein, including defining data structures stored in RAM 946and modifying such data structures according to the processes defined bythe software. In addition or as an alternative, the computer system canprovide functionality as a result of logic hardwired or otherwiseembodied in a circuit (for example: accelerator 944), which can operatein place of or together with software to execute particular processes orparticular parts of particular processes described herein. Reference tosoftware can encompass logic, and vice versa, where appropriate.Reference to a computer-readable media can encompass a circuit (such asan integrated circuit (IC)) storing software for execution, a circuitembodying logic for execution, or both, where appropriate. The presentdisclosure encompasses any suitable combination of hardware andsoftware.

While this disclosure has described several exemplary embodiments, thereare alterations, permutations, and various substitute equivalents, whichfall within the scope of the disclosure. It will thus be appreciatedthat those skilled in the art will be able to devise numerous systemsand methods which, although not explicitly shown or described herein,embody the principles of the disclosure and are thus within the spiritand scope thereof.

The invention claimed is:
 1. A method for video decoding, the methodcomprising: decoding a binary coded coding unit (CU) address carrying anidentification of a CU in a network abstraction layer (NAL) unit headercomprising fixed length codewords; determining, based on decoding thebinary coded CU address in the NAL unit header, that the CU address isincluded in a list of CUs to be decoded; and reconstructing a CU basedon determining that the CU address is included in the list of CUs to bedecoded, wherein the NAL unit header includes only a nal_unit_typesyntax element that indicates a type of data that a NAL unit carries, anuh_cu_address syntax element that indicates a CU address, and anuh_temporal_id_plus1 syntax element that indicates a temporal layer ofa coded picture to which the NAL unit belongs.
 2. The method of claim 1,wherein, for a given frame, each CU in the frame has a unique CUaddress, and the unique CU address is assigned in accordance with a scanorder of a picture segment in the frame.
 3. The method of claim 2,wherein the scan order is associated with a top left corner, and isincreased by one following a top-to-bottom, right-to-left order.
 4. Themethod of claim 1, wherein the CU address is in a fixed position in theNAL unit header.
 5. The method of claim 1, wherein a size of the CUaddress is determined through a predefined value of a high level syntaxstructure syntax element in the same NAL unit header.
 6. The method ofclaim 1, wherein a size of the CU address is determined through at leastone syntax element in a parameter set, the parameter set being activefor the picture to which the NAL unit header belongs.
 7. A device fordecoding a video sequence, the device comprising: at least one memoryconfigured to store program code; at least one processor configured toread the program code and operate as instructed by the program code, theprogram code including: decoding code configured to cause the at leastone processor to decode a binary coded CU address carrying anidentification of a CU in a network abstraction layer (NAL) unit headercomprising fixed length codewords; determining code configured to causethe at least one processor to determine, based on decoding the binarycoded CU address in the NAL unit header, that the CU address is includedin a list of CUs to be decoded; and reconstructing code configured tocause the at least one processor to reconstruct a CU based ondetermining that the CU address is included in the list of CUs to bedecoded, wherein the NAL unit header includes only a nal_unit_typesyntax element that indicates a type of data that a NAL unit carries, anuh_cu_address syntax element that indicates the CU address, and anuh_temporal_id_plus1 syntax element that indicates a temporal layer ofa coded picture to which the NAL unit belongs.
 8. The device of claim 7,wherein, for a given frame, each CU in the frame has a unique CUaddress, and the unique CU address is assigned in accordance with a scanorder of a picture segment in the frame.
 9. The device of claim 8,wherein the scan order is associated with a top left corner, and isincreased by one following a top-to-bottom, right-to-left order.
 10. Thedevice of claim 7, wherein the CU address is in a fixed position in theNAL unit header.
 11. The device of claim 7, wherein a size of the CUaddress is determined through a predefined value of a high level syntaxstructure syntax element in the same NAL unit header.
 12. The device ofclaim 7, wherein a size of the CU address is determined through at leastone syntax element in a parameter set, the parameter set being activefor the picture to which the NAL unit header belongs.
 13. Anon-transitory computer-readable medium storing instructions, theinstructions comprising: one or more instructions that, when executed byone or more processors of a device, cause the one or more processors to:decode a binary coded CU address carrying an identification of a CU in anetwork abstraction layer (NAL) unit header comprising fixed lengthcodewords; determine, based on decoding the binary coded CU address inthe NAL unit header, that the CU address is included in a list of CUs tobe decoded; and reconstruct a CU based on determining that the CUaddress is included in the list of CUs to be decoded, wherein the NALunit header includes only a nal_unit_type syntax element that indicatesa type of data that a NAL unit carries, a nuh_cu_address syntax elementthat indicates the CU address, and a nuh_temporal_id_plus1 syntaxelement that indicates a temporal layer of a coded picture to which theNAL unit belongs.